“Refsdal” Meets Popper: Comparing Predictions of the Re-Appearance of the Multiply Imaged Supernova Behind MACSJ1149.5+2223

Abstract

Supernova "Refsdal," multiply imaged by cluster MACS1149.5+2223, represents a rare opportunity to make a true blind test of model predictions in extragalactic astronomy, on a timescale that is short compared to a human lifetime. In order to take advantage of this event, we produced seven gravitational lens models with five independent methods, based on Hubble Space Telescope (HST) Hubble Frontier Field images, along with extensive spectroscopic follow-up observations by HST, the Very Large and the Keck Telescopes. We compare the model predictions and show that they agree reasonably well with the measured time delays and magnification ratios between the known images, even though these quantities were not used as input. This agreement is encouraging, considering that the models only provide statistical uncertainties, and do not include additional sources of uncertainties such as structure along the line of sight, cosmology, and the mass sheet degeneracy. We then present the model predictions for the other appearances of supernova "Refsdal." A future image will reach its peak in the first half of 2016, while another image appeared between 1994 and 2004. The past image would have been too faint to be detected in existing archival images. The future image should be approximately one-third as bright as the brightest known image (i.e., H 25.7 AB » mag at peak and H 26.7 AB » mag six months before peak), and thus detectable in single-orbit HST images. We will find out soon whether our predictions are correct.

Lens models under the microscope: comparison ofHubble Frontier Fieldcluster magnification maps

“…This SN was strongly lensed both by the cluster and also by a single cluster member galaxy, resulting in four distinct images in an "Einstein Cross" configuration. Measurement of the time delays and relative magnifications between these first four images allowed a similar test of lens model accuracy (Rodney et al 2016;Treu et al 2016). The reappearance of SN Refsdal with a fifth image more widely spaced from the initial four is now offering another opportunity to confront lens model predictions with a pencil-beam test (Kelly et al 2016).…”

Sn Refsdal: Photometry and Time Delay Measurements of the First Einstein Cross Supernova

“…Lens models consistently indicate that the second image of this galaxy, 1.2, is a trailing image (e.g., Kelly et al 2015c;Oguri 2015;Sharon & Johnson 2015;Treu et al 2016), and indeed a new transient source appeared at the expected location in 2015 December. This new source is consistent with being the predicted reappearance image, SX (Kelly et al 2015b).…”

“…The earliest models, first posted within a week of the SN Refsdal discovery, are shown as squares (Oguri 2015;Sharon & Johnson 2015). 30 The recently updated model of Jauzac et al (2016) is plotted with circles, and the set of models from the Treu et al (2016) model comparison program (Die-a, Gri-g, Ogu-a, Ogu-g, Sha-a, Sha-g, Zit-g, Zit-c) are plotted with trangles.…”

“…Subsequently, other lens modeling groups have produced updated models, taking advantage of improved imaging and spectroscopic data on this field to generate models using better catalogs of multiply-imaged galaxies, as well as better precision in reproducing those strong-lensing constraints Jauzac et al 2016). Most recently, Treu et al (2016) presented a coordinated effort from five lens modeling groups to produce new MACS J1149.6+2223 lens models with a set of collectively vetted strong lensing constraints. The individual results from each group are being published separately, providing details on each group's modeling approach Kawamata et al 2015;J.…”

“…Treu et al (2016) describes the collaborative development of some of these updated lens models by five independent teams, and highlights the rare opportunity for a true blind test of these models. By generating these predictions in advance of the reappearance of SN Refsdal as image SX, the modelers have provided falsifiable predictions that can be directly confronted with a true measurement of the time delays and magnification ratios.…”